1. Field of the Invention
The present invention relates to a copier capable of reduction and/or enlarged copying (hereinafter referred to as varied-size copying) as well as real-size copying.
2. Description of the Prior Art
There is already known a copier capable of real-size copying and varied-size copying. In such known copier the rate of change in size of copying sheet is selected equal to that of the change in magnification of image. Also the switching from real-size copying to a varied-size copying is achieved, in case of a single lens, by displacing said lens along the optical axis thereof, or, in case of a zoom lens, by displacing the zooming portion thereof along the optical axis thereof. There usually accompanies a displacement of the lens in a direction perpendicular to the optical axis. This is because the supply of copy sheets of different sizes is usually achieved in such a manner that a side edge thereof always advances along the same line, so that there will result a positional aberration between the image of the original and the copying sheet unless the lens is dislaced in a direction perpendicular to the optical axis.
Also there is already known a copier which provides, along a side edge of copying sheet, a non-imaging portion of a determined width in which the image of the original is not recorded. Such non-imaging portion results from the presence of a separating means, for example a separating belt, positioned on one side between the copying sheet and a photosensitive member on which a toner image is formed, for separating said copying sheet from said photosensitive member after the image is transferred onto said copying sheet, as image transfer is not realized in a portion of a width of several to ten millimeters corresponding to the width of said separating means even if a toner image is formed in said portion. Otherwise, in case it is desirable to have a margin of a determined width along a side edge of the copying sheet, such margin or non-imaging portion can be obtained by rendering a portion of the photosensitive member corresponding to said margin insensitive to light.
Such copier providing a non-imaging portion inevitably provides, in real-size copying, an image which is incomplete along a side edge thereof. Also in varied-size copying, in such conventional copier, a similar incomplete image is obtained since the rate of change in size of copying sheet is selected equal to that of change in magnification of image. The percentage of incomplete image becomes larger as the reduction rate of the image is increased, since the size of non-imaging portion remains constant.